Sternal Closure Device with Dual Locking Mechanism

ABSTRACT

A sternal closure device includes an insertion member, a receiver member and a joint locking mechanism. The joint locking mechanism includes a dual pawl assembly and a dual ratchet assembly. The dual pawl assembly includes a pair of pawl arms that include heads with outward facing teeth. The dual ratchet assembly includes a pair of ratchet arms with inward facing teeth that are configured for an intermeshed engagement with the teeth on the corresponding pawl arms. Alignment tabs on the ratchet arms are captured within guide channels on the receiver member. The configuration and number of the teeth contribute to the strength of the device. The locking mechanism contributes to efficiency, speed, and strength of the closure.

RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional PatentApplication Ser. No. 62/790,409 entitled “Sternal Closure Device withDual Locking Mechanism” filed Jan. 9, 2019, the disclosure of which isherein incorporated by reference.

FIELD OF INVENTION

The present invention relates generally to surgical positioning devicesand more particularly to a surgical device for capturing, positioning,aligning, and stabilizing portions of a severed human sternum.

BACKGROUND OF INVENTION

Wire closures are widely represented in the contemporary art as arecognized means for closing the sternum following a mid-linesternotomy. Wire-based closure devices nonetheless suffer from severaldeficiencies. First, the average implementation/deployment time is 15-20minutes per wire closure. Such an excessive time requirement translatesinto increased operating room costs, increased doctor, staff andinsurance costs, and increased doctor fatigue. Second, a variety ofdisruptive forces frustrate the very intention of wire-based systems.Third, the current plating systems fail to provide three-dimensionalstabilization of the fractured sternal segments thereby allowingdisplacement of the segments. Anatomic forces associated withsternotomies include the rectus abdominus muscles exerting an uneven andshearing displacement pull, a lateral and diagonal pull by pectoralismuscles, forces generated by Valsalva action and anterior/posteriordisplacement by intervertebral muscles of the hemi-sternum viarespiratory muscle action.

In view of the deficiencies of wire-based clamping and plating surgicaldevices, and further in view of the life threatening conditionsassociated with failure of such devices, newer clamp closure technologyhas been recognized as superior to the traditional wire closure systems.These devices recognize the three dimensional forces at work in ananatomically moving system and stabilize in a superior fashion.Circumferential clamp closures typically include two primary elementsthat can be removably associated with one another. As in U.S. Pat. No.6,051,007 issued Apr. 18, 2000 to Hogendijk et al., (“Hogendijk '007”),several prior art clamp closures include two clamp elements that eachinclude a “leg” portion configured to grasp an opposing side of avertically severed sternum. When approximated, the two clamp elementsdraw the severed sternum into a closed position, and stabilize thesternum in a three dimensional fashion. A locking feature is used tohold the clamp closures in the approximated position.

Although generally effective, prior art clamp closures suffer severaldeficiencies. For example, many locking mechanisms used in prior artclosures fail under increased stress loads. Other locking mechanisms aredifficult to manipulate or impossible to quickly remove under emergencyconditions. Other devices possess multiple parts or segments which mustbe articulated, and spot welded, thus increasing chances of devicefailure. It is to these and other deficiencies in the prior art that thepresent invention is directed.

SUMMARY OF THE INVENTION

A sternal closure device includes an insertion member, a receiver memberand a joint locking mechanism. The joint locking mechanism includes adual pawl assembly and a dual ratchet assembly. The dual pawl assemblyincludes a pair of pawl arms that include heads with outward facingteeth. The dual ratchet assembly includes a pair of ratchet arms withinward facing teeth that are configured for an intermeshed engagementwith the teeth on the corresponding pawl arms. Alignment tabs on theratchet arms are captured within guide channels on the receiver member.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a front perspective view of a sternal closure deviceconstructed in accordance with an embodiment of the present invention.

FIG. 2 is a top view of the sternal closure device of FIG. 1.

FIG. 3 is a side view of the sternal closure device of FIG. 3.

FIG. 4 is an end view of the sternal closure device of FIG. 1.

FIG. 5 is a top view of the receiver member of the sternal closuredevice of FIG. 1.

FIG. 6 is a side view of the receiver member of FIG. 5.

FIG. 7 is an end view of the receiver member of FIG. 5.

FIG. 8 is a top perspective view of the receiver member of FIG. 5.

FIG. 9 is a top view of the insertion member of the sternal closuredevice of FIG. 1.

FIG. 10 is a side view of the insertion member of FIG. 5.

FIG. 11 is an end view of the insertion member of FIG. 5.

FIG. 12 is a top perspective view of the insertion member of FIG. 5.

FIG. 13A is a close-up view of a portion of the teeth on a firstembodiment of the insertion member of FIG. 5.

FIG. 13B is a close-up view of a portion of the teeth on a secondembodiment of the insertion member of FIG. 5.

FIG. 14A is a top view of a single-leg embodiment of the sternal closuredevice.

FIG. 14B is a side view of the single leg embodiment of FIG. 14A.

FIG. 14C is an end view of the single leg embodiment of FIG. 14A.

FIG. 14D is a cross-sectional view of the single leg embodiment of FIG.14A.

FIG. 15A is top view of the insertion member of the single legembodiment of FIG. 14A.

FIG. 15B is a top perspective view of the insertion member of the singleleg embodiment of FIG. 14A.

WRITTEN DESCRIPTION

FIGS. 1-4 and FIGS. 14A-14D provide various views of a sternal closuredevice 100 constructed in accordance with an exemplary embodiment. Thesternal closure device 100 can be generally characterized as a two-piecearticulating clamp in which a receiver member 102 engages with aninsertion member 104. The receiver member 102 and insertion member 104are presented as distinct, separable components. When joined together,the insertion member 104 is retained within the receiver member 102 in alocking relationship as the insertion member 104 is advanced within thereceiver member 102. The receiver and insertion members 102, 104 aresecured together by a joint locking mechanism 106 that prevents theinsertion member 104 from being withdrawn from the receiver member 102except when the joint locking mechanism 106 is intentionally released byan operator. The receiver member 102, which may be characterized as a“female” clamp portion, is illustrated in isolation in FIGS. 5-8 andFIGS. 16A-16B. The insertion member 104, which may be characterized as a“male” clamp portion, is illustrated in isolation in FIGS. 9-13 andFIGS. 15A-15B.

As disclosed below, the sternal closure device 100 includes a number ofcomponents that cooperatively perform the intended function ofpositioning, aligning and securing a severed sternum. It will beunderstood that although the present disclosure explicitly coversvarious embodiments, there are additional embodiments that are alsoencompassed within the scope of the present invention. It will befurther understood that the sternal closure device 100 can be sized andconfigured for use on patients across a wide range of sizes andvariations in anatomies. Unless otherwise noted, each component of thesternal closure device 100 is constructed from a suitable surgical-grademetal alloy, ceramic or hardened plastic.

The receiver member 102 includes a receiver member base 108, one or morereceiver member legs 110 and a dual pawl assembly 112. The receivermember legs 110 extend downward and forward from the back of thereceiver member base 108. In the embodiments depicted in FIGS. 1-12, thereceiver member legs 110 are spaced apart by a distance (d1) that can besized and configured to capture a rib. In the embodiments depicted inFIGS. 16A-16B, the receiver member 102 includes a single receiver memberleg 110 that is sized and configured to fit between a pair of ribsattached to the severed sternum.

The receiver member base 108 includes rounded shoulders 109 above thereceiver member legs 110. The rounded shoulders 109 improve comfort andreduce the risk of wound dehiscence. The receiver member legs 110 mayeach include feet 114 that are configured to contact a posterior side ofthe sternum. The receiver member legs 110 may also include a texturedsurface 116 that is configured to increase frictional contact with alateral portion of the sternum. Thus, as best seen in FIGS. 3, 6 and14B, the receiver member base 108 and receiver member legs 110 cooperateto form a crescent or “C-shape” that is sized and configured to captureand partially surround approximately one half of the severed sternum.

The dual pawl assembly 112 includes a pawl block 118 that extends upwardfrom the top surface of the receiver member base 108. Pawl arms 120extend forward from the top of the pawl block 118. As illustrated inFIG. 7, the pawl block 118 raises the pawl arms 120 above the topsurface of the receiver member base 108. Each pawl arm 120 includes ahead 122 located on the distal end of the pawl arm 120. The head 122includes a series of outward facing pawl teeth 124 and a tool aperture126. As illustrated in FIG. 5, the pawl arms 120 and heads 122 arelaterally spaced apart.

In exemplary embodiments, each component of the dual pawl assembly 112is constructed from a metal or metal alloy that permits the pawl arms120 to slightly deflect inward when a sufficient lateral force isapplied to the outside of the pawl arms 120, or when a sufficientcompressive force is applied to the pawl arms 120 through the toolapertures 126 in the pawl heads 122. The lateral force can be applied bythe insertion member 104 when the insertion member 104 is engaged withinthe receiver member 102. The lateral compressive force can also beapplied to the pawl arms 120 by engaging release pliers (not shown) inthe tool apertures 126.

In exemplary embodiments, the dual pawl assembly 112 is manufactured asunitary, integral component together with the balance of the receivermember 102. In these embodiments, the dual pawl assembly 112 ispermanently fixed to, or made as part of, the receiver member base 108.In other embodiments, the pawl block 118 can be configured forattachment to the receiver member base 108 by removable fasteners, suchas a stud and lock-nut mechanism.

The receiver member 102 further includes channels 128 that extend alongthe top of the receiver member base 108. The channels 128 extendsubstantially parallel to the pawl arms 120. The channels 128 can bemanufactured as part of a unitary component of the receiver member base108. In this way, the entire receiver member 102 can be manufactured asunitary piece through milling, casting, forging or additivemanufacturing processes. As best indicated in FIGS. 7-8, the channels128 include an upper overhang that cooperates with the receiver memberbase 108 to form a boxed receiver that has lower, side and upper wallsthat are configured to receive and capture the insertion member 104.

Turning to FIGS. 9-13 and FIGS. 15A-15B, shown therein are isolatedviews of the insertion member 104. The insertion member 104 includes aninsertion member base 130, one or more insertion member legs 132 and adual ratchet assembly 134. The insertion member 104 includes roundedshoulders 111 above the insertion member legs 132. The rounded shoulders111 improve comfort and reduce the risk of wound dehiscence. The one ormore insertion member legs 132 extend downward and forward from the backof the insertion member base 130. In the embodiment depicted in FIGS.9-13, the insertion member 104 includes a pair of insertion member legs132 that are spaced apart by a distance (d2). In some embodiments, thedistance (d2) between the insertion member legs 132 is sized to surrounda rib attached to the severed sternum. The distance (d2) between theinsertion member legs 132 can be larger, smaller or the same size as thedistance (d1) between the receiver member legs 110. In the single-legembodiment depicted in FIGS. 15A-15B, the insertion member 104 includesa single insertion member leg 132 that can be sized and configured tofit between a pair of ribs attached to the severed sternum.

The insertion member legs 132 may each include feet 136 that areconfigured to contact a posterior side of the sternum. The insertionmember legs 132 may also include a textured surface 138 that isconfigured to increase frictional contact with a lateral portion of thesternum. Thus, as best seen in FIGS. 3, 10 and 14B, the insertion memberbase 130 and insertion member legs 132 cooperate to form a crescent or“C-shape” that is sized and configured to capture and partially surroundapproximately one half of the severed sternum.

The dual ratchet assembly 134 includes a pair of ratchet arms 140 thatextend forward from the insertion member base 130. Each of the ratchetarms 140 includes a linear rack consisting of a series of inward facingratchet teeth 142 disposed on the interior side of each ratchet arm 140.FIG. 13A provides a close-up view of a first embodiment of the ratchetteeth 142. In this embodiment, the ratchet teeth 142 have anasymmetrical profile that permits advancement of the ratchet arms 140 ina forward direction, but resists retraction in a reverse direction. Arelief 146 is located at the interior intersection between adjacentteeth 142. The relief 146 may facilitate the disengagement of the teeth142 from the pawl teeth 124. The size, shape and number of ratchet teeth142 may vary with application. Increasing the number of ratchet teeth142 increases the number of positions in which the insertion member 104can be secured within the receiver member 102. Increasing the depth ofthe ratchet teeth 142 increases the amount of deflection needed torelease the pawl arms 120 from the ratchet arms 140. FIG. 13B presents aclose-up view of a second embodiment of the ratchet teeth 142. In thisembodiment, the ratchet teeth 142 do not include an interspersed relief146 between each tooth 142. The embodiment depicted in FIG. 13B may beeasier and more cost-effective to manufacture, while providing a fullengagement with the corresponding pawl teeth 124.

In exemplary embodiments, the geometry and configuration of the pawlteeth 124 is configured to match the geometry and configuration of theratchet teeth 142. In both cases, each of the teeth 124, 142 isconfigured with sides that form acute angle. In some embodiments, theteeth 124, 142 each form a point with an angle less than 40°. In someembodiments, the sides of the teeth 124, 142 are positioned at about a37° angle, with a slightly rounded tip (as best illustrated in FIGS. 13Aand 13B). As illustrated in FIGS. 2 and 8, the heads 122 include aplurality of pawl teeth 124. In the embodiment depicted, each head 122includes four pawl teeth 142. The use of multiple pawl teeth 142increases the total contact area between the pawl teeth and the ratchetteeth 142 within the joint locking mechanism 106 to provide a stronger,more secure engagement between the receiver member 102 and the insertionmember 104. The aggregate contact area is also increased as a result ofthe steep angle and length of each tooth within the pawl teeth 124 andratchet teeth 142.

Each of the ratchet arms 140 includes an outward facing alignment tab144 located on the exterior side of each ratchet arm 140. The alignmenttabs 144 are sized and configured to fit closely within the channels 128of the receiver member base 108. In exemplary embodiments, the extensionof the alignment tabs 144 from the ratchet arms 140 contributes to eachratchet arm 140 having a substantially “L-shaped” cross section. Theclose fit between the alignment tabs 144 and the channels 128 preventsthe insertion member 104 from rotating, tilting or lifting off thesurface of the receiver member base 108. In this way, the channels 128,base 108 and alignment tabs 144 cooperatively restrict the relativemovement between the insertion member 104 and receiver member 102 to asingle linear longitudinal axis.

The joint locking mechanism 106 includes the combination of elementsfrom the dual pawl assembly 112 and the dual ratchet assembly 134.Unlike prior art clamp-style sternal closure devices that employrotating locks or spring-based ratchet systems, the joint lockingmechanism 106 sternal closure device 100 includes a robust lockingengagement between the dual pawl assembly 112 and dual ratchet assembly134 that reduces the risk of unintentional separation or disengagementbetween the receiver member 102 and insertion member 104.

During use, the insertion member 104 and receiver member 102 contactopposing portions of the severed sternum. As the sternum isapproximated, the insertion member 104 is introduced into the receivermember 102. The alignment tabs 144 of the ratchet arms 140 are capturedwithin the channels 128 of the receiver member 102. As the insertionmember 104 further advances into the receiver member 102, the dualratchet assembly 134 engages the dual pawl assembly 112 to prevent theretraction of the insertion member 104 from the receiver member 102. Asthe insertion member 104 advances, the ratchet arms 140 force the pawlarms 120 to deflect inward against an opposing, outward-biased springforce produced by the pawl arms 120. Once the ratchet arms 140 arecaptured by the channels 128 and engaged with the heads 122 of the pawlarms 120, the pawl arms 120 apply the outward spring force against theratchet arms 140. The pawl teeth 124 on the heads 122 of the pawl arms120 are thus forced into an intermeshed connection with the ratchetteeth 142 on the ratchet arms 140. The orientation and configuration ofthe ratchet teeth 142 and pawl teeth 124 prevent the withdrawal of theinsertion member 104 (as best illustrated in FIG. 2), and increase theclosing strength and stability of the insertion member 104 while mated.

Importantly, the joint locking mechanism 106 increases the lockedengagement of the dual pawl assembly 112 and the dual ratchet assembly134 when the insertion member 104 and receiver member 102 are placed intension. The orientation and configuration of the pawl teeth 124 andratchet teeth 142 increase the outward lateral force applied by the pawlheads 122 against the ratchet arms 140, which is then transferred to,and opposed by, and the channels 128. In this way, an increasing tensionforce across the sternal closure device 100 caused by coughing or deepinhalation increases the engagement forces within the joint lockingmechanism 106. The receiver member 102 and insertion member 104 aredesigned such that increased tensional forces are translated intoincreased lateral engagement forces through the joint locking mechanism106 and captured within the channels 128 of the receiver member 102.This represents a significant improvement over prior art locking devicesthat rely on single-sided locking mechanisms or dual locking mechanismsthat are not captured within a boxed receiver.

To release the insertion member 104, the dual pawl assembly 112 must bedisengaged from the ratchet arms 140. The dual pawl assembly 112 can beselectively released by an operator by applying a compressive force tothe heads 122 of the pawl arms 120 to cause the heads to deflect inwardby a distance greater than the depth of the engagement between theratchet teeth 142 and the pawl teeth 124. In exemplary embodiments, arelease tool with a hinged plier mechanism is connected to the toolapertures 126 in the heads 122 so that leverage can be used to apply acompressive force sufficient to disengage the pawl teeth 124 on theheads 122 from the ratchet teeth 142 on the ratchet arms 140. Once thedual pawl assembly 112 has been released from the dual ratchet assembly134, the insertion member 104 can be easily withdrawn from the receivermember 102.

It is clear that the present invention is well adapted to carry out itsobjectives and attain the ends and advantages mentioned above as well asthose inherent therein. While embodiments of the invention have beendescribed in varying detail for purposes of disclosure, it will beunderstood that numerous changes may be made which will readily suggestthemselves to those skilled in the art and which are encompassed withinthe spirit of the invention disclosed herein and in the associateddrawings and appended claims.

It is claimed:
 1. A sternal closure device comprising: a receivermember, wherein the receiver member comprises a dual pawl assembly; andan insertion member, wherein the insertion comprises a dual ratchetassembly that is configured for capture within the receiver member. 2.The sternal closure device of claim 1, wherein the receiver membercomprises: a receiver member base; channels extending along the receivermember base; and one or more receiver member legs extending from thereceiver member base.
 3. The sternal closure device of claim 2, whereinthe receiver member comprises rounded shoulders above the one or morereceiver member legs.
 4. The sternal closure device of claim 2, whereinthe dual pawl assembly comprises: a pawl block; and a pair of pawl armsextending from the pawl block.
 5. The sternal closure device of claim 4,wherein the dual pawl assembly further comprises a pair of heads,wherein each of the pair of heads is located at a distal end of acorresponding one of the pair of pawl arms.
 6. The sternal closuredevice of claim 5, wherein each of the heads comprises: a plurality ofoutward facing pawl teeth; and a tool aperture.
 7. The sternal closuredevice of claim 6, wherein the insertion member comprises: an insertionmember base; and one or more insertion member legs extending from theinsertion member base.
 8. The sternal closure device of claim 7, whereinthe insertion member comprises rounded shoulders above the one or morereceiver member legs.
 9. The sternal closure device of claim 7, whereinthe dual ratchet assembly further comprises a pair of ratchet arms. 10.The sternal closure device of claim 9, wherein each of the pair ofratchet arms comprises: an outward facing alignment tab, wherein thealignment tab is configured to be received by a corresponding one of thechannels on the receiver member; and a series of inward facing ratchetteeth, wherein the ratchet teeth are configured for an intermeshedengagement with the pawl teeth of a corresponding one of the pair ofheads.
 11. A sternal closure device comprising: a receiver member,wherein the receiver member comprises: a receiver member base; a pair ofreceiver member legs extending from the receiver member base; a pair ofrounded shoulders, wherein each of the pair of rounded shoulders islocated above a corresponding one of the pair of receiver member legs;and a dual pawl assembly; and an insertion member, wherein the insertioncomprises: an insertion member base; a dual ratchet assembly that isconfigured for engagement with the dual pawl assembly of the receivermember; a pair of insertion member legs extending from the insertionmember base; and a pair of rounded shoulders, wherein each of the pairof rounded shoulders is located above a corresponding one of the pair ofinsertion member legs.
 12. The sternal closure device of claim 11,wherein the dual pawl assembly comprises: a pawl block; and a pair ofpawl arms extending from the pawl block.
 13. The sternal closure deviceof claim 12, wherein the dual pawl assembly further comprises a pair ofheads, wherein each of the pair of heads is located at a distal end of acorresponding one of the pair of pawl arms.
 14. The sternal closuredevice of claim 13, wherein each of the heads comprises a plurality ofoutward facing pawl teeth.
 15. The sternal closure device of claim 11,wherein the dual ratchet assembly further comprises a pair of ratchetarms.
 16. The sternal closure device of claim 15, wherein the receivermember further comprises: channels extending along the receiver memberbase; and one or more receiver member legs extending from the receivermember base.
 17. The sternal closure device of claim 16, wherein each ofthe pair of ratchet arms comprises: an outward facing alignment tab,wherein the alignment tab is configured to be received by acorresponding one of the channels on the receiver member; and a seriesof inward facing ratchet teeth, wherein the ratchet teeth are configuredfor an intermeshed engagement with the pawl teeth of a corresponding oneof the pair of heads.
 18. A sternal closure device comprising: areceiver member; an insertion member; and means for releasably securingthe insertion member within the receiver member.
 19. The sternal closuredevice of claim 18, wherein the receiver member comprises: a receivermember base; and a pair of receiver member legs extending downward fromthe base and configured to engage a first side of a severed sternum. 20.The sternal closure device of claim 19, wherein the insertion membercomprises: an insertion member base; and a pair of insertion member legsextending downward from the insertion member base and configured toengage a second side of a severed sternum.